1. Field of the Invention
This invention relates to a printer, and more particularly to a serial printer in which a recording head is reciprocated in a predetermined direction against a recording medium such as paper so that recording is performed successively on a recording medium by such movement.
2. Description of the Prior Art
Although this type of printer is widely used because of its low price, such printers involve extremely complex operations for the initial setting of fan-fold paper that has perforations between sheets, for the positioning of the leading edges of cut sheets, and the positioning in a left-to-right direction of such recording papers.
Printers are known that overcome these defects having various auto-paper setting functions, but these printers have the defects of an extremely complex mechanism and high cost.
FIG. 1 shows an arrangement of a conventional printer.
In FIG. 1, reference numeral 101 denotes a platen. A recording head 102 is disposed opposite the platen 101. A paper hold roller 103 is in contact with the recording head 102 side of the platen 101 at an upper position. The paper hold roller 103 is installed rotatably on a shaft 104. The shaft 104 is supported at both ends by arms 105.
The bottom edges of the arms 105 are fixed to a rotatable shaft 109 that also acts as a guide shaft for a carriage. The shaft 109 is fixed to a top edge of a lever 113. A bottom edge of the lever 113 is coupled to a rod 112a of a solenoid 112.
A paper pan 106 is disposed underneath the platen 101. A pinch roller 107 is disposed underneath the paper pan 106. A supporting shaft 108 of the pinch roller 107 applies force to approach the platen 101 side by a spring (not shown). The pinch roller 107 passes through an opening 106A formed by the paper pan 106, and comes into contact with the platen 101.
A paper-edge setting lever 110 is disposed substantially below the platen 101 underneath the paper pan 106 with one of its ends fixed to a shaft 111.
The edge of the paper-edge setting lever 110 comes into contact with the platen 101 through the opening 106A formed by the paper pan 106. As described below, the edge of the paper-edge setting lever 110 touches the edge of a recording paper 114a or 114b and keeps that edge parallel to a shaft 101a of the platen 101.
To the other side of the platen 101, a pin-wheel 117 is disposed at a predetermined distance from the paper pan 106. The pin-wheel 117 has a plurality of pins 117a disposed around its circumference. The pin-wheel 117 is fixed to a shaft 119.
Reference numeral 114a denotes a fan-fold paper which has feed holes as shown in FIG. 11B as reference numeral 56h that engage with the pins 117a formed along both edges at pitch. The pins 117a are engageable in these holes 56 h.
After the fan-fold paper 114a has been set on the pin-wheel 117, it is held down by a cover 118 so that it does not come away from the pins 117a.
A paper guide 115 is disposed on top of the paper pan 106. The paper guide 115 guides a cut sheet 114b and has a positioning member 116 that aligns with the width of the paper 114b slidably mounted at one end.
Reference numeral, 106a denotes a paper pan for cut sheet paper 114b.
Recording paper is set on to the above arrangement as follows.
First, to set a cut sheet 114b, the positioning member 116 is slid to a predetermined position to align with the gradations on the paper guide 115. Then, an off-line switch or the like on a keyboard (not shown) is pressed, so that the printer is in an off-line mode with respect to a host device for instance.
Next, a paper set lever (not shown) is rotated, and the pinch roller 107 is moved away from the platen 101. At this time, the paper-edge setting lever 110 engages and presses on the platen 101.
Next, through the paper guide 115, the cut-sheet 114b is inserted between the paper pan 106a and the platen 101, and is stopped against the paper-edge setting lever 110. Next, the paper set lever is operated, so that the pinch roller 107 presses against the platen 101, and the cut-sheet 114b is held between the platen 101 and the roller 107.
When the paper set key on the keyboard is pressed in this condition, current is supplied to the solenoid 112 so that a rod 112a is drawn in, and the arm 105 is rotated in the clockwise direction in the drawing through a lever 113, and the paper hold roller 103 moves away from the platen 101.
At the same time, the paper-edge setting lever 110 also moves away from the platen 101. Next, after the platen 101 rotates in a counterclockwise direction in the drawing, and the cut-sheet 114b has been fed for a predetermined distance, the current to the solenoid 112 is interrupted, and the paper hold roller 103 presses against the platen 101 holding the edge of the recording paper.
Then, the setting of the cut sheet paper 114b is completed.
The procedure for setting cut-sheet paper 114b as described above involves the following steps:
(1) Pressing the off-line switch. PA1 (2) Operating the paper set lever. PA1 (3) Inserting the recording paper. PA1 (4) Operating the paper set lever. PA1 (5) Pressing the paper set key.
Consequently, conventional printers are expensive due to their complex mechanisms, and are relatively difficult to operate because of the complicated operation involved.
To set the fan-fold paper 114a, a lock-lever (not shown) is released, the pin-wheel 117 is slid along the shaft 119 , the cover 118 is opened, the holes 56h along both edges of the fan-fold paper 114a are aligned with the pin 117a and the cover 118 is closed. The space between the pin-wheels 117 is adjusted so that the fan-fold paper 114a does not crumple, and then the lock lever is operated to lock the pin-wheels 117.
Next, the paper set lever (not shown) is operated, and the pinch roller 107 moves away from the platen 101. At this time, the paper-edge setting lever 110 does not engage.
Then, the paper hold roller 103 is lifted manually, and after the off-line switch (not shown) is pressed, the line-feed button is pressed to rotate the pinwheel 117 and the fan-fold paper 114a is fed until it passes the paper hold roller 103.
In this condition, bringing down the paper hold roller 103 manually, and operating the paper feed knob (not shown) in an appropriate forward feed direction or a reverse feed direction aligns the position of the edge of the fanfold paper 114a and completes the setting.
If the power supply is turned off when the setting of the fan-fold paper 114a has been completed and the printer is reset, referring the position of the edge of the fan-fold paper 114a each page will be fed to a top of form by a form-feed switch or a program according to a paper length set by a DIP (dual-in-line package) switch or a program.
However, setting of the fan-fold paper 114a involves many manual operations for aligning the position of pin-wheel 117 or the position of the top edge of the paper 114a with gradations or by guess-work, resulting in an extremely complex operation.
Furthermore, after setting the paper 114a, feeding the paper 114a forwards or backwards even once with the paper feed knob misaligns the standard of the top edge of the fan-fold paper 114a, so that the page will not feed to the top of the form correctly thereafter.
Moreover, because conventional printers require a drive means such as a solenoid 112 to move the paper hold roller 103 away from the platen 101, the construction becomes complicated and excessive electrical power is required so that both the price of the device itself and the operating costs are high.
Furthermore, on printers which use an ink ribbon in the recording system, an arm or other guide member for guiding the ink ribbon close to the recording head 102 is fitted to an ink ribbon cassette which accomodates the ink ribbon, so that the ink ribbon cassette has a large overall size and requires a large amount of storage space, and safety and operability are impaired by the arm or other guide member knocking against other members.
Moreover, on printers for multi-colored printing that use multi-colored ink ribbons, a complex arrangement is required for the selection of the color. Because such printers also require a drive source such as a solenoid to operate the mechanism, they are expensive because of the large number of parts required.